The present invention relates to a magnetoresistive head having a pair of shield layers disposed so as to sandwich a magnetoresistive film, and a multi-channel type magnetic head having a plurality of the magnetoresistive heads.
FIG. 6 shows a related magnetoresistive head 100 (hereinafter called as an MR head 100). The MR head 100 is provided with a magnetoresistive element 101 (hereinafter called an MR element 101) as a magnetic sensor element. The MR element 101 is configured by a magnetoresistive film 102 (hereinafter called an MR film 102) which changes its resistance value with respect to a sense current in accordance with the change of magnetizing direction and a pair of electrodes 103 for supplying a sense current to the MR film 102.
The MR head 100 is further provided with an upper shield layer 104 and a lower shield layer 105 which are disposed so as to sandwich the MR element 101 from the upper and lower direction, respectively. The upper shield layer 104 and the lower shield layer 105 sandwich the MR element through non-magnetic insulation films 106. The non-magnetic insulation films 106 prevent a current flowing into the MR film 102 from being shunt and flowing into the upper shield layer 104 and the lower shield layer 105.
Further, the MR head 100 includes an inductive head 107 as a recording element. In the inductive head 107, an upper pole layer 109 is formed on the upper shield layer 104 through a gap film 108. A coil portion 111 covered by an insulation film 110 is formed at a portion surrounded by the upper shield layer 104 and the upper pole layer 109. That is, in the inductive head 107, the upper shield layer 104 and the upper pole layer 109 constitute a magnetic core, whereby recording magnetic field is generated between the upper shield layer 104 and the upper pole layer 109 which are abutted to each other through the gap film 108.
In the MR head 100 thus configured, the MR element 101 detects magnetic field generated from a magnetic recording medium to thereby reproduce information recorded on the magnetic recording medium. In the MR film 102, the magnetizing direction changes by the magnetic field generated from the magnetic recording medium, so that a resistance value thereof with respect to the sense current is changed. In the MR head 100, since the sense current is supplied so as to be constant, the change of the resistance value of the MR film 102 can be detected as the voltage change with respect to the sense current.
However, the MR head 100 can detect smaller magnetic field as compared with the case where the reproduction is performed by using the inductive head 107, and the MR film 102 can be formed quite thinly by the thin film technique. Thus, a magnetic recording medium on which information is recorded at a high density can be reproduced by using the MR head. Accordingly, the MR heads 100 have been frequently employed in the hard disc driving apparatuses of computer apparatuses and so partially contribute to the high-density recording of the hard disc driving apparatuses.
In recent years, the MR heads 100 have been applied not only to the hard disc driving apparatuses but also to apparatuses for recording/reproducing a tape-shaped magnetic recording medium. In the latter case, information recorded on the tape-shaped magnetic recording medium is reproduced by using the MR head 100. Thus, high-density recording can be promoted in the tape-shaped magnetic recording medium like the hard disc driving apparatus.
However, when the MR head 100 is applied to the recording/reproducing apparatus for a tape-shaped magnetic recording medium, the tape-shaped magnetic recording medium slides on and scrapes against the MR head 100 at a high speed to thereby cause static electricity, so that the MR film 102 is charged with static electricity. Since the MR element 101 is sandwiched between the upper shield layer 104 and the lower shield layer 105 through the non-magnetic insulation film 106, the static electricity discharges due to voltage differences caused between the MR film 102 and the upper shield layer 104 and/or the lower shield layer 105, whereby the MR element may be broken. When the MR element 101 is broken, the MR head can not be used any more.
In this manner, the MR head 100 has a problem that electrostatic breakage is likely occurred between the MR film 102 and the upper shield layer 104 and/or the lower shield layer 105. In particular, this problem becomes more remarkable when the MR head 100 is used for a tape-shaped magnetic recording medium.
It is therefore an object of the invention is to provide an MR head which can surely prevent the occurrence of electrostatic breakage between an MR element and shield layers.
In order to achieve the above object, according to the present invention, there is provided a magnetoresistive head, comprising:
a first shield layer;
a first non-magnetic layer, formed on the first shield layer;
a magnetoresistive element, including a magnetoresistive film and an electrode portion both formed on the first non-magnetic layer;
a second non-magnetic layer, formed on the magnetoresistive element;
a second shield layer, formed on the second non-magnetic layer;
a non-magnetic metal layer, for electrically connecting the first shield layer and the second shield layer;
a first earth member, electrically connected to the electrode portion of the magnetoresistive element;
a second earth member, electrically connected to the first shield layer and the second shield layer; and
a third earth member, electrically connected to the first earth member and the second earth member.
In this configuration, since the first and the second earth members are coupled to the common third earth member, the electric potential of the magnetoresistive element and the shield layers are always made identical. Therefore, occurrence of the electrostatic breakage can be prevented so that recording and reproduction can be performed stably and reliably.
Preferably, the first, the second and the third earth members are made of a material having a higher resistance value than an entire resistance value of the magnetoresistive element.
In this configuration, a sense current supplied to the magnetoresistive film can be prevented from being shunt into the earth members.